A wide range of printers produce printed documents from digital image data. In some instances, the digital image data represent one or more printed pages and the printer reproduces the printed pages during a print job. Some printers are also configured to merge two or more digital images together to produce a printed page that includes portions of each of the digital images. For example, in a merge operation, the printer merges an overlay digital image over a background digital image to form a single printed page with the overlay digital image merged with the background. The printer merges the image data for both the background image and the digital image to form a composite merged image prior to printing the final document. Document processing systems enable an operator to select two or more digital images and to arrange the digital images on a page in a wide range of configurations.
While existing printers can produce printed output from a combination of multiple digital images, limitations in the processing of the digital data can limit the options for how multiple digital images can be combined in a printed document. For example, many printers form images on a line-by-line basis based on a series of linear sets of binary data, which are commonly denoted as raster image data. A printer that combines two different digital images forms the raster image data with portions of both images that are arranged in the appropriate locations along the line. Existing printers can have limited resolution in positioning an overlay image on a background image in the raster line. For example, one existing printer aligns digital data only at addresses in the raster image line that are evenly divisible by sixteen bits. The digital image data can only be moved by a number of pixels corresponding to the sixteen-bit increment, resulting in a limited number of options for aligning two digital images together during a merge operation. Consequently, improvements to the manipulation of digital data in a printer to form combined printed images with improved alignment precision would be beneficial.